The parent invention relates to a new, novel flexible polyurethane foam having the feel and comfort properties of latex foam and which is suitable for cushioning because of its unique softness and to a method of making such foam utilizing a new combination of polyether polyols. The foam of the invention has an Indentation Force Deflection (25% IFD) as low as 3 lbs.
Attempts have been made in the prior art to produce soft, flexible foams, but none of these foams achieves the xe2x80x9cfeelxe2x80x9d and comfort of latex foam in which the 25% IFD is as low as 3 lbs.
The Pastor, et al. U.S. Pat. No. 3,405,077 discloses a process for making polyurethane foams having improved softness, flexibility and hand, wherein a known polyether polyol has incorporated therein from 1.8 to 5 parts of water by weight and a mono-, di- or trihydric alcohol. The mixture is reacted with a polyisocyanate in the presence of a volatile alkane as blowing agent. In the Table at the top of column 4, Foam A is disclosed as having an IFD 25% value of 16 and is described as an xe2x80x9cunusually soft, open-cell porous, flexible polyether urethane foam having a low IFD value.xe2x80x9d
The Westfall, et al. U.S. Pat. No. 4,883,825 discloses a process for making low density, flexible polyurethane foams. As set forth in column 2, beginning with line 45, such 5 foams, having a density of 1 to 2 pounds per cubic foot, are formed by the reaction of (1) high reactivity, high ethylene oxide, high functionality polyols, (2) hydrophilic polyhydric compounds, (3) water above 4.0 parts per hundred parts and (4) organic polyisocyanates. The polyisocyanates used in the Tables have an index of from 100 (Tables IV, V and VII-X) to 110 (Table VI). IFD values are only set forth in Table X and they are 25 and 45. The patentee is not seeking to form foams having IFD values comparable to those of latex foam.
The Nichols, et al. U.S. Pat. No. 4,929,646 discloses polyurethane foams made using high molecular weight (at least 5,000) high functionality poly(oxyethylene) compounds (at least 50 weight percent oxyethylene units) as cell openers, which are effective in softening foams made using MDI-based polyisocyanates. As set forth in column 6, when the polyisocyanate is MDI, it should have an average functionality of 1.5 to about 2.2 (column 7, lines 5-22). The isocyanate index for MDI is from 60-100 with 70-103 being more preferred. Highly resilient foams are formed at indices as low as about 60. (See column 7, lines 48-56.) The IFD values are set forth and compared in Table V. While the patents state at the top of column 13 that excellent improvement in cell opening is obtained along with a desirable softening of the foam, as indicated by decreasing IFD values, such values in Table V appear to be very high.
The Hager, U.S. Pat. No. 4,950,694 discloses the preparation of low density, low resilience, soft, flexible polyurethane foams having a substantially open cell structure by reacting a conventional hydroxyl-containing polyether polyol with a polyisocyanate having an isocyanate index of between 60 and 94. The patent uses a foam processing aid to stabilize the foam to allow processing the foam substantially free of inert blowing agents. The foam processing aid is a combination of a cross-linker and a cell opener. This technology is known in the industry for reducing or eliminating auxiliary blowing agents. High resiliency foams are discussed in column 2, and they are usually produced using high ethylene oxide content polyols having equivalent weights above about 1,600 and primary hydroxyl contents of about 50% (column 2, lines 43-46). The foams have a 25% IFD value of less than 35, preferably below about 25 and more preferably below about 20 lbs. per 50 square inches (column 5, lines 10-14). IFD values are shown in the Tables for the respective polyurethanes, but none are under 11 and almost all are between 11 and 20.
The Consoli U.S. Pat. No. 4,144,386 discloses a method of producing flexible polyurethane foams having allegedly excellent softness by the reaction of a polyhydroxyl containing polyether, described in column 2 beginning with line 15, with a polyisocyanate which is the product of the partial polymerization of toluene diisocyanate and polyhydroxyl containing polyether. The molar ratio of isocyanate groups to hydroxyl groups is equal to or greater than 1 and preferably between 1:1 to 1.15:1. The load bearing capacity Kg/322 cm2, at 25% is 2.8-6.3 in Table 1 (column 4) and from 2.5-5.4 in Table 2 (column 5).
The Lehmann U.S. Pat. No. 4,981,880 discloses a method of making low density, soft, flexible polyurethane foams by reacting polyisocyanate with a polyol composition containing at least two different hydroxyl-containing compounds in the presence of a trimerization catalyst and a blowing agent. At least one of the hydroxyl compounds is a polyol of hydroxyl number from 20 to 120 and at least one hydroxy compound is a polyether mono-alcohol. The latter polyol is present in an amount sufficient to provide measurably softer foams (column 4, line 9-12). As stated in column 7, lines 11-19, increasing amounts of trimerization catalyst provide for softer foam exhibiting lower compressive load deflection. Alkanes, and particularly pentane, are disclosed as supplementary blowing agents (column 7, lines 62-64). The properties of the foams are set forth in Tables 2 and 4 (column 11).
Hager, in his U.S. Pat. No. 5,011,908, states that prior to his invention of low density (less than about 1.8 pcf) and/or low load (less than 20 pounds/50 square inch), the production of high resiliency foam had been limited (column 1, line 59 to column 2, line 4). Also, production of such foams required the use of halocarbons (column 3, lines 11-15). Hager also states that all commercially useful systems for producing high resilience foam rely on polymer polyols and omission of such polymer polyols results in severe shrinkage (column 2, lines 42-55). Hager""s invention utilizes a polymer polyol composition containing (1) a high functionality polyol, (2) a subsidiary poly (alkylene oxide) high in poly (oxyethylene) content, and (3) a stably dispersed polymer (column 3, lines 60-65). The latter polymer can be standard vinyl polymer or copolymer, a polyurea-type polymer or a condensation product of a polyfunctional low molecular weight glycol or glycol amine with a diisocyanate (column 5, lines 26-35). The isocyanate index is from about 100 to 115 (column 8, lines 55-57). The IFD values set forth in the several tables, at 25% load, are greater than 12. The patent focuses on modifying the polymer polyol to provide stable, non-shrinking, free-rise foam with high water levels, but requires the use of cross-linkers to achieve this end.
It is also known in the art to react a mixture of known polyols (Arcol Polyol 1280, 4,000 M.W. and Arcol Polyol 1230, 4,500 M.W.), namely, polyoxypropylene/polyoxyethylene triols with TDI (toluene diisocyanate) having an isocyanate index value of less than 50 to produce a supersoft foam of about 6 lbs. IFD. However, the resulting foam does not possess the xe2x80x9cfeelxe2x80x9d associated with a latex foam and is not a latex-like polyurethane foam.
The novel flexible polyurethane foam of the invention having latex-like properties of xe2x80x9cfeelxe2x80x9d and comfort is formed by reacting a mixture of polyether polyols consisting essentially of (a) a major proportion of a triol polyol having a primary hydroxyl content of about 50-80% with about a 10-25% ethylene oxide cap and a molecular weight (M.W.) of about 3,000-6,500, (b) a minor proportion of a grafted polymer triol polyol having about 3,000-6,500 M.W. and (c) a very minor amount of a triol polyol having a primary hydroxyl content of at least about 50% and about 40-90% ethylene oxide cap, and reacting the triol polyol mixture with an isocyanate having a functionality within the range of about 2.0-2.7 and an Isocyanate Index of about 75-100. The reaction takes place in the presence of a critical amount of water and an auxiliary blowing agent.